Handling a wafer during processing steps may be difficult because of a fragility of the wafer. Another difficulty may arise from the fact that a wafer, in particular a reconstituted wafer, is subject to warpage.
A carrier which is temporarily bonded to the wafer can enhance the stability during handling and may straighten a warped wafer. The carrier may be debonded from the wafer after performing all necessary processing steps. For temporarily bonding a temporary carrier to the wafer a temporary adhesive may be used.
Temporary adhesives, e.g. in the form of adhesive films, are frequently used in semiconductor industry. Temporary adhesives in the meaning of this application are adhesives which are intended to bond two components only temporarily together. Known temporary adhesives are operative in a temperature range starting from about room temperature (20° C.) up to about 180° C., 200° C. or sometimes up to about 250° C. Often, the higher temperatures are only supported during a short time period without debonding. Additionally, even lower temperatures, i.e. temperatures below 180° C. may lead to a debonding if a mechanical force acts upon the adhesive layer. Two different mechanisms are used for temporary adhesives. Temporary adhesives either have a low adhesive force which allows an easy mechanical debonding or they allow for a controlled destruction of their adhesive force. Both mechanisms may also be combined. Known destruction mechanisms comprise, for example, chemically dissolving the temporary adhesive, destroying/decreasing the adhesive force by heat with temperatures above the designated temperature range or by radiation.
Temporary adhesives may have the disadvantage that conditions encountered during processing the wafer may deactivate the adhesive force of the temporary adhesive or at least severely reduce the adhesive force. A low adhesive force may not be sufficient to straighten a warped wafer and/or to hold a wafer securely during all processing steps. For these and further reasons there is a need for the present invention.